Temperature and Humidity (again)

[Bor Gullet]

Sorry, I've read over a dozen threads on this - but I didn't actually see many answers in them...

Are the environmental operating conditions for the Teensy 3.2 or LC known? We want to use them outdoors in Orlando, so heat and humidity are the most relevant difficulties. We can protect them from water though.

I did see this test, where there were issues going from -10 to 40C, but I gather that might be due to the rapid change of temperature under test:

https://forum.pjrc.com/threads/29108-Teensy-operating-temperature

 

[tonton81]

just pickup a dht22, they have a wide temp range which wont affect humidity/temp values (much)

 

[Bor Gullet]

Thanks tonton,

I'm actually asking what the thermal and humidity limits of the Teensy itself are. What is the maximum temperature and humidity we can expose it to and still get reliable operation?

 

[BJB]

Will assume for various technical and legal reasons, PJRC has not included specific tabulation of environmental specifications. And, as this is a 'systems' question, will have to be a DIY thing.

This is what my evil little mind did some years ago, when men were men and doggies did not wear scarfs. Start with the basic processor specs here, then tabulate a BoM from the schematic. You will have to guess as the ratings for the passive components.

Some general rules of thumb and forefinger and wrist.
- PCBs with V-0 flammability are typically rated 130C.
- derate per your system-level voltage and current input, and power consumption.
- derate per enclosure sun load.
- determine what components and materials could be hygroscopic.
- humidity for non-sensor and display stuff is non-effective issue if non-condensing.
- PCB and component residual stress greatly reduces environmental immunity.
- 5/50 rule -> if at least 5 year life span, 50% margin for all operational and environmental parameters. (not available for all Teensy 3.1,3.2 components (dunno about 3.5,3.6).
- Empirical test data trumps component spec sheets. Test your box to extinction, resurrect it, then test again.
- intermittent operations is not your friend. continuous power is thine savior.

A customer had a box (with a T3.1) in Pascagoula, Mississippi. Power applied for continuously for 14 months with no problem until the Navy decided ram the dock. Freezing rain dripped in through a broken connector and cracked the enclosure.

 

[Bor Gullet]

Great advice BJB. I think your point about empirical data is the one that stands out. We will do as much real world testing as we can in the SoCal sun, get some heat lamps, ship one to the client site and ask them to run our test program...

Cheers!